1. Field of the Invention
The present invention relates generally to skateboards and skate devices such as quad wheel roller skates, multi-wheel scooters, and to casters and caster devices such as scooters, caster boards, wheelchairs and utility carts. More particularly, the invention concerns both dual wheel and single wheel axle support mechanisms and casters with novel suspension mechanisms designed to absorb shock. Also disclosed is an embodiment for an extendable tilt axis alignment device for a truck hanger enabling full tilt steering functions when a truck hanger is mounted on a biased suspension mechanism.
2. Description of Related Art Including Information Disclosed Under 37 CFR 1.97 and 1.98
Skateboards of various designs having a pair of trucks in opposing orientation disposed under a rider surface are well known in the art. The prior art trucks are typically fitted with a pair of wheels with steering being accomplished by the rider tilting the rider surface, thus pivoting the hangers on a tilt axis between 30° and 55°, rotating axles and wheels in opposite directions thus causing the board to turn. Two types of kingpin configurations for skateboard trucks are predominate in prior art. The first is the conventional kingpin truck consisting of a hanger that tilts on a kingpin which acts as the fulcrum for the hanger. The kingpin is mounted approximately perpendicular to the tilt axis through a central aperture of the hanger with the kingpin being fixedly attached to a mounting base. The hanger has a central alignment leg projecting in a transverse direction from the axle that maintains the tilt axis and is received by a pivot cup that is an articulation point in the mounting base. The hanger tilts along the axis and resistively compresses resilient tilt-crush bushings that bring the hanger back to a neutral position. The second is the torsion kingpin truck that consists of a hanger that tilts on a kingpin that is located longitudinally on the tilt axis so that the hanger can tilt on the kingpin to permit steering the truck. Various torsion mechanisms have also been disclosed that provide resistance to tilting and function to assist in bringing the hanger back to a neutral position.
Prior art designs of non-biased casters often include a U-shaped wheel fork with a transversely mounted axle having a single wheel disposed on the axle and located between the arms of the wheel fork. Another form of prior art caster is the split wheel caster which has a central body portion with a transversely mounted axle passing through the central body and projecting on both sides to receive two wheels. Though the split wheel caster has two wheels, it effectively performs in the same manner as a single wheel caster.
Prior art designs of non-biased axle support mechanisms for the skateboard and caster provide adequate performance over smooth surfaces, but can become extremely hazardous when a wheel of the device encounters an obstacle such as a small rock or minor curb transition. Because the prior art devices have no effective means to absorb the shock of the impact with a rock or curb transition, the rider can either be ejected from the device or dangerously lose control of the device.
For over a century, many types of biased suspension mechanisms have been suggested to absorb shock and provide the user with a more compliant and safer passage over irregular terrain. However, none of these prior art devices have been able to provide the novel attributes of the present invention regarding shock absorption, stability, functionality and weight.
By way of example, a biased skateboard truck with a conventional kingpin configuration is disclosed in U.S. Pat. No. 4,155,565 issued to de Caussin et al. The de Caussin device includes a truck that is mounted onto a separate biased plate-shaped member which comprises a duplication of the base structure and the biasing means and results in additional weight and undesirable added axle height thereby limiting functionality.
Another prior art truck construction with a conventional kingpin configuration and suspension mechanism is disclosed in U.S. Publication No. 2008/0252026A to Kang. In the Kang device, a biased plate-shaped member supports a hanger that is a non-extendable link between opposing inwardly facing independent arms. With this construction, when a force is applied to the truck, the arms bind and negate each other's movement and shock-absorbing potential.
U.S. Pat. No. 4,152,001 issued to Christianson, discloses an axle hanger that is mounted on a plate-shaped member. The Christianson device has the ability to conform to the terrain, but lacks a steering alignment mechanism to enable the hanger to maintain the steering tilt axis. Accordingly, the hanger is susceptible to axial forces that could cause loss of the integrity of the steering geometry and stability.
U.S. Pat. No. 7,219,907 to Chang concerns a torsion kingpin truck configuration that has a suspension mechanism but has limitations due to the independent movement of the axles as the bottom of the central body can scrape the ground if the suspension is compressed, thus requiring large wheels to avoid this undesirable condition.
U.S. Pat. No. 1,745,992 issued to Herold discloses a caster that compresses an elastomeric damper in a nutcracker fashion. The Herold device exhibits a very limited compression stroke and suffers unavoidable deterioration of the elastic damper due to repeated impact.
The prior art U.S. Pat. No. 2,738,542 issued to Clark discloses a rather commonly adopted suspension mechanism for a caster and includes a saddle-shaped mounting bracket, a U-shaped wheel fork, a hinge pin and two helical coil springs. However, the Clark device is unduly complex in that it incorporates many separate components in addition to the biasing means to support the mechanism, adding additional cost and weight to the caster assembly.
U.S. Pat. No. 5,394,589 issued to Braeger et al. discloses a somewhat simpler shock-absorbing caster, but uses multiple structural components not required in the novel apparatus of the present invention.